Rotary pump and brake device having the same

ABSTRACT

A rotary pump includes a first side plate and a second side plate between which an outer rotor and an inner rotor are arranged. The second side plate has a concave portion on a surface adjacent to a maximum gap portion relative to a drive shaft. The concave portion is located in an outer teeth passing section which is defined between a line on which a teeth tip of an outer teeth part of the inner rotor passes in response to rotation of the inner rotor and a line on which a teeth bottom of the outer teeth part of the inner rotor passes in response to rotation of the inner rotor. The concave portion communicates with one of a plurality of gap portions while the inner rotor is rotated.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2012-281303 filed on Dec. 25, 2012, the disclosure of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to a rotary pump and a brake device having the rotary pump.

BACKGROUND

An inscribed-gear rotary pump such as trochoid pump has an inner rotor, an outer rotor and a casing. The inner rotor has an outer teeth part around the outer perimeter, and the outer rotor has an inner teeth part around the inner perimeter. The casing has a first side plate, a second side plate, and a central plate, and the outer rotor and the inner rotor are arranged in the casing in a manner that the inner teeth part and the outer teeth part mesh with each other such that plural gap portions are defined between the inner teeth part and the outer teeth part.

In such a rotary pump, it is necessary to seal a space between a high pressure part and a low pressure part. The first side plate has a seal component which is pressed onto one axial surface of the rotary pump for the sealing, and the other axial surface is directly pressed onto the second side plate for achieving the mechanical sealing. The central plate has a concave portion in which a seal component is arranged, and the seal component is in contact with the outer perimeter of the outer rotor for the sealing.

However, if the pressing force from the rotors to the respective side plates becomes large, loss in the rotational torque becomes large, since the mechanical sealing is adopted. If heat is generated at the mechanical sealing, the heated part may expand, and the expansion may reduce the pump discharge capability.

JP 4007080 B (US 2003/0227216 A1) describes that a discharge groove is defined on a side plate at positions corresponding to the plural gap portions into which discharge pressure is introduced, so as to reduce the loss in the rotational torque. Thus, the outer rotor and the inner rotor can be pressed back toward the seal component by the discharge pressure on the surface adjacent to the mechanical sealing, so the frictional resistance can be reduced between the axial end surface of the outer rotor and the end surface of the side plate. Therefore, the loss in the rotational torque can be reduced between the respective rotors and the side plate, and the pump discharge capability can be restricted from being lowered.

However, friction is also generated at positions not corresponding to the plural gap portions. For this reason, it is required to further reduce the contact resistance at the mechanical sealing between the side plate and the respective rotor.

SUMMARY

It is an object of the present disclosure to provide a rotary pump in which contact resistance and wear amount are reduced between a casing and a rotor. It is another object of the present disclosure to provide a brake device having the rotary pump.

According to a first example of the present disclosure, a rotary pump includes a rotary portion, a casing and a seal component. The rotary portion includes an outer rotor having an inner teeth part on an inner perimeter, and an inner rotor having an outer teeth part on an outer perimeter. The inner rotor has a rotation axis corresponding to a drive shaft. A plurality of gap portions is defined between the inner teeth part and the outer teeth part and has a maximum gap portion which has a maximum volume among the plurality of gap portions. The casing covers the rotary portion and has a first side plate and a second side plate between which the outer rotor and the inner rotor are arranged and a central plate arranged to surround an outer perimeter of the outer rotor. The second side plate has a contact surface in contact with the outer rotor and the inner rotor so as to achieve a mechanical sealing. The casing has an intake port through which fluid is drawn into the rotary portion and a discharge port through which fluid is discharged from the rotary portion. The seal component is arranged between the first side plate and the rotary portion to define a low pressure part connected to the intake port and a high pressure part connected to the discharge port. The second side plate has a concave portion on the contact surface adjacent to the maximum gap portion relative to the drive shaft. The concave portion is located in an outer teeth passing section which is defined between a line on which a teeth tip of the outer teeth part of the inner rotor passes in response to rotation of the inner rotor and a line on which a teeth bottom of the outer teeth part of the inner rotor passes in response to rotation of the inner rotor. The concave portion communicates with one of the plurality of gap portions while the inner rotor is rotated.

Thus, since the concave portion is defined in the end surface of the second side plate, when the concave portion and the gap portion communicate with each other, the brake fluid contained in the gap portion is supplied into the concave portion. Thereby, it becomes possible to make the brake fluid intervene between the second side plate and the inner rotor, and the brake fluid functions as lubricating oil. Thus, the frictional resistance of the contact part between the second side plate and the inner rotor can be reduced. Therefore, it becomes possible to decrease the amount of wear between the second side plate and the inner rotor.

According to a second example of the present disclosure, the concave portion is located in an inner teeth passing section which is defined between a line on which a teeth tip of the inner teeth part of the outer rotor passes in response to rotation of the outer rotor and a line on which a teeth bottom of the inner teeth part of the outer rotor passes in response to rotation of the outer rotor, and the concave portion communicates with one of the plurality of gap portions while the inner rotor is rotated.

Similarly, when the concave portion and the gap portion communicate with each other, the brake fluid contained in the gap portion is supplied into the concave portion. Thereby, it becomes possible to make the brake fluid intervene between the second side plate and the outer rotor, and the brake fluid functions as lubricating oil. The frictional resistance of the contact part between the second side plate and the outer rotor can be reduced. Therefore, it becomes possible to decrease the amount of wear between the second side plate and the outer rotor.

The concave portion communicates with only the one of the plurality of gap portions, and does not simultaneously communicate with the plurality of gap portions. Therefore, the compression performance can be prevented from being lowered in the gap portions.

According to a third example of the present disclosure, the concave portion is located in an overlap area in which the outer teeth passing section and the inner teeth passing section overlap with each other

According to a fourth example of the present disclosure, a brake device includes the rotary pump, a brake fluid pressure generator which generates a brake fluid pressure based on a depression force, a braking force generator which generates a braking force to a wheel based on the brake fluid pressure, a main conduit connected to the brake fluid pressure generator to transmit the brake fluid pressure to the braking force generator, and an auxiliary conduit connected to the brake fluid pressure generator to supply brake fluid to the main conduit so as to raise the braking force generated by the braking force generator. The rotary pump is arranged to draw the brake fluid at the intake port from the brake fluid pressure generator through the auxiliary conduit and to discharge the brake fluid at the discharge port toward the braking force generator through the main conduit.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings:

FIG. 1 is a view illustrating a brake device having a rotary pump according to a first embodiment;

FIG. 2A is a cross-sectional view illustrating the rotary pump;

FIG. 2B is a cross-sectional view taken along a line IIB-O-IIB of FIG. 2A;

FIG. 2C is a cross-sectional view taken along a line IIC-IIC of FIG. 2B;

FIG. 3 is an enlarged view illustrating the rotary pump in which a concave portion is defined in a second side plate;

FIG. 4 is an enlarged view illustrating a comparative example of the concave portion;

FIG. 5 is a cross-sectional view illustrating a rotary pump according to a second embodiment;

FIG. 6 is an enlarged view illustrating the rotary pump of the second embodiment in which a concave portion is defined in a second side plate; and

FIG. 7 is a cross-sectional view illustrating a rotary pump according to a third embodiment.

DETAILED DESCRIPTION

Embodiments of the present disclosure will be described hereafter referring to drawings. In the embodiments, a part that corresponds to a matter described in a preceding embodiment may be assigned with the same reference numeral, and redundant explanation for the part may be omitted. When only a part of a configuration is described in an embodiment, another preceding embodiment may be applied to the other parts of the configuration. The parts may be combined even if it is not explicitly described that the parts can be combined. The embodiments may be partially combined even if it is not explicitly described that the embodiments can be combined, provided there is no harm in the combination.

(First Embodiment)

A brake device is explained with reference to FIG. 1. The brake device is applied to a vehicle equipped with a hydraulic circuit of a diagonal piping system having a first pipe connecting wheel cylinders of a front-right wheel and a rear-left wheel and a second pipe connecting wheel cylinders of a front-left wheel and a rear-right wheel. Alternatively, the brake device may be applied to other system, other than the diagonal piping system, such as straight pipe connecting a front part and a rear part.

As shown in FIG. 1, a brake pedal 1 is connected to a booster 2 that boosts brake depression force. The booster 2 has a pushrod which transmits the boosted depression force to a master cylinder (M/C) 3. M/C pressure is generated when the pushrod presses a master piston of the M/C 3. The M/C pressure is transmitted to a wheel cylinder (W/C) 4 for the front-right wheel FR, and a wheel cylinder (WIC) 5 for the rear-left wheel RL through an actuator which controls the brake fluid pressure so as to perform antilock brake system (ABS) control. A master reservoir 3 a is connected to the MIC 3, and supplies brake fluid to the M/C 3 or stores extra brake fluid.

The brake pedal 1, the booster 2, and the M/C 3 may correspond to a brake fluid pressure generator. The W/C 4 and the W/C 5 may correspond to a braking force generator.

The following explanation is based on a first piping system which connects the front-right wheel FR to the rear-left wheel RL. The explanation for a second piping system (SPS) which connects the front-left wheel FL to the rear-right wheel RR is omitted, which is similar to the explanation for the first piping system.

The brake device is equipped with a main conduit A connected to the M/C 3. A differential pressure control valve 22 and a check valve 22 a are arranged in the main conduit A. The differential pressure control valve 22 is controlled by a brake electrical control unit (ECU). The main conduit A is divided into two parts at the differential pressure control valve 22. Specifically, the main conduit A has a first conduit Al which receives the M/C pressure in a section from the M/C 3 to the differential pressure control valve 22, and a second conduit A2 in a section from the differential pressure control valve 22 to each of the W/C 4 and the W/C 5.

The differential pressure control valve 22 is usually in the communicating state. In a case where the M/C pressure is lower than a predetermined pressure, when the W/C 4 and the W/C 5 are suddenly braked, or when in the traction control, the differential pressure control valve 22 generates a predetermined pressure difference between the section of the M/C 3 and the section of the W/C 4, 5 (in the differential state). The differential pressure control valve 22 can linearly adjust a preset value set for the differential pressure.

Moreover, the second conduit A2 is further branched to two parts. A pressure increase control valve 30 for controlling an increase of brake fluid pressure of the W/C 4 is installed to one of the branched conduits and a pressure increase control valve 31 for controlling an increase of brake fluid pressure of the W/C 5 is installed to the other of the branched conduits.

The pressure increase control valve 30, 31 is a two-position valve capable of controlling communication and shut-off states by the brake ECU. When the two-position valve is controlled to a communicating state, the M/C pressure or a brake fluid pressure produced by a pump 10 can be applied to the respective W/C 4, 5. In the normal braking operation where the ABS is not controlled by the ECU, each of the pressure increase control valves 30 and 31 is always controlled in the communicating state as a normally-open valve.

Safety valves 30 a and 31 a are installed in parallel to the pressure increase control valves 30 and 31, respectively. The safety valve 30 a or 31 a allows the brake fluid to swiftly return from the W/C 4 or 5 to the M/C 3 when the ABS control has been finished by stopping depression of the brake pedal 1.

Pressure reduction control valve 32 or 33 capable of controlling communication and shut-off states by the brake ECU is arranged at an intake conduit B connecting the second conduit A2 between the pressure increase control valve 30 or 31 and the W/C 4 or 5 to a pressure control reservoir 40. In the normal braking operation where the ABS control is not operated, the pressure reduction control valves 32 and 33 are always brought into a shut-off state as normally-close valve.

A rotary pump 10 is arranged in an auxiliary conduit C which connects the main conduit A between the differential pressure control valve 22 and the pressure increase control valve 30, 31 to the pressure control reservoir 40. The discharge port side of the rotary pump 10 is equipped with a safety valve 10A which prohibits the brake fluid from flowing backward. A motor 11 is connected to the rotary pump 10, and the rotary pump 10 is driven by the motor 11.

An auxiliary conduit D is defined to connect the pressure control reservoir 40 to the M/C 3, and a two-position valve 23 is arranged in the auxiliary conduit D. The two-position valve 23 is a normally-close valve which is closed at a normal time, and is driven at a brake assistance time or at a traction control time. At this time, the two-position valve 23 is in the communicating state to change the auxiliary conduit D into the communicating state. Further, the rotary pump 10 is operated in the state where the pressure difference is maintained by the pressure difference control valve 22 between the M/C 3 and the W/C 4, 5. Thereby, the brake fluid of the first conduit Al is drawn up through the auxiliary conduit D, and is discharged out to the second conduit A2. Therefore, the pressure in the W/C 4, 5 can be made higher than the M/C pressure, such that the wheel braking force can be increased.

The pressure control reservoir 40 controls the pressure difference between the brake fluid pressure in the reservoir and the M/C pressure, and supplies the brake fluid to the rotary pump 10. The pressure control reservoir 40 has reservoir holes 40 a and 40 b which communicate with a reservoir chamber 40 c of the pressure control reservoir 40. The reservoir hole 40 a is connected to the auxiliary conduit D, and receives the brake fluid flowing from the M/C 3. The reservoir hole 40 b is connected to the intake conduit B and the auxiliary conduit C, and receives the brake fluid discharged from the W/C 4, 5 and supplies the brake fluid to the intake side of the rotary pump 10.

On the inner side of the reservoir hole 40 a, a valve object 41 such as ball valve is arranged. The communication or interception state between the auxiliary conduit D and the reservoir chamber 40 c is controlled by the separation or the seating of the valve object 41 relative to a valve seat 42. The pressure difference between the inner pressure in the reservoir chamber 40 c and the M/C pressure is controlled by controlling a distance between the valve seat 42 and the valve object 41.

A rod 43 is provided on the lower side of the valve object 41 as a separate object separated from the valve object 41. The rod 43 has a predetermined stroke for moving the valve object 41 up and down. A piston 44 and a spring 45 are disposed in the reservoir chamber 40 c. The piston 44 is interlocked with the rod 43. The spring 45 generates power which pushes out the brake fluid from the reservoir chamber 40 c by pressing the piston 44 toward the valve object 41.

When a predetermined quantity of the brake fluid is stored in the pressure control reservoir 40, the valve object 41 is seated on the valve seat 42, such that the brake fluid cannot flow into the pressure control reservoir 40. For this reason, brake fluid which exceeds the suction ability of the rotary pump 10 does not flow into the reservoir chamber 40 c, so high pressure is not impressed to the intake side of the rotary pump 10.

The rotary pump 10 is described with reference to FIGS. 2A-2C and FIG. 3. FIGS. 2A-2C correspond to the rotary pump 10 in FIG. 1. FIG. 2A is a cross-sectional view taken along a line IIA-IIA in FIG. 2B. FIG. 2B is cross-sectional view taken along a line IIB-O-IIB in FIG. 2A. FIG. 2C is a cross-sectional view taken along a line IIC-IIC in FIG. 2B.

The rotary pump 10 is a trochoid pump which is an internal gear pump. As shown in FIGS. 2A-2C, the rotary pump 10 is arranged in a rotor chamber 50 a defined in a casing 50. An outer rotor 51 and an inner rotor 52 are contained in the rotor chamber 50 a of the casing 50. The outer rotor 51 and the inner rotor 52 are assembled in the casing 50 in a state where respective center axes (point X and point Y in the drawing) are shifted from each other. The outer rotor 51 is provided at its inner periphery with an inner teeth portion 51 a. The inner rotor 52 is provided at its outer periphery with an outer teeth portion 52 a. The inner teeth portion 51 a of the outer rotor 51 and the outer teeth portion 52 a of the inner rotor 52 are in mesh with each other and form a plurality of gap portions 53.

As is apparent from FIG. 2A, the rotary pump 10 is a multiple teeth trochoid type pump having no partition plates (crescent) in which the gap portions 53 are formed by the inner teeth portion 51 a of the outer rotor 51 and the outer teeth portion 52 a of the inner rotor 52. The inner rotor 52 and the outer rotor 51 share a plurality of contact points (that is, contact faces) at the mesh faces in order to transmit rotation torque of the inner rotor 52 to the outer rotor 51.

As shown in FIG. 2B, the casing 50 includes a first side plate 71, a second side plate 72 and a central plate 73, which define the rotor chamber 50 a. The outer rotor 51 and the inner rotor 52 are arranged between the first side plate 71 and the second side plate 72. The central plate 73 is placed between the first side plate 71 and the second side plate 72, and has a bore in which the outer rotor 51 and the inner rotor 52 are housed. The central plate 73 is positioned to surround the outer periphery of the outer rotor 51. A minute clearance S is formed between the outer perimeter of the outer rotor 51 and the inner perimeter of the central plate 73, and brake fluid flows into the minute clearance S.

As shown in FIG. 2B, the first and second side plates 71 and 72 are respectively provided at their center portions with center bores 71 a and 72 a which communicate with the rotor chamber 50 a. A drive shaft 54 fitted to the inner rotor 52 is housed in the center bores 71 a and 72 a. The outer rotor 51 and the inner rotor 52 are rotatably arranged in the bore of the central plate 73. That is, a rotating unit constituted by the outer rotor 51 and the inner rotor 52 is rotatably contained in the rotor chamber 50 a of the casing 50. As shown in FIG. 2A, the outer rotor 51 rotates with a point X as a rotation axis and the inner rotor 52 rotates with a point Y as a rotation axis.

When a line running on both the point X and the point Y respectively corresponding to the rotation axes of the outer rotor 51 and the inner rotor 52 is defined as a center line Z of the rotary pump 10 in the cross-section shown in FIG. 2A, an intake port 60 and a discharge port 61 both of which communicate with the rotor chamber 50 a are formed on the left and right sides of the center line Z in the first side plate 71. The intake port 60 and the discharge port 61 are arranged respectively at positions communicating with the plurality of gap portions 53. The brake fluid from outside can be sucked into the gap portions 53 via the intake port 60 and the brake fluid in the gap portions 53 can be discharged to outside via the discharge port 61.

There exist a maximum gap portion 53 a where the brake fluid volume is the largest and a minimum gap portion 53 b where the brake fluid volume is the smallest among the plurality of the gap portions 53. The maximum and minimum gap portions 53 a and 53 b communicate neither with the intake port 60 nor with the discharge port 61. The maximum and minimum gap portions 53 a and 53 b serve to hold pressure difference between the intake pressure at the intake port 60 and the discharge pressure at the discharge port 61.

As shown in FIG. 2A, the inner wall surface of the central plate 73 is provided with a concave portion 73 a and a concave portion 73 b recessed outward in the radial direction of the outer rotor 51, at the positions advanced by about 45 degrees from the center line Z toward the intake port 60 centering on the point X which is the rotation axis of the outer rotor 51. A first sealing member 80 and a second sealing member 81 are respectively installed in the concave portions 73 a and 73 b to restrain the brake fluid from flowing from the high pressure outer circumference to the low pressure outer circumference.

The first sealing member 80 consists of a rubber component 80 a which has a spherical or approximately cylinder shape, and a resin component 80 b which has a rectangular parallelepiped shape. The resin component 80 b is biased or pressed by the rubber component 80 a to be brought into contact with the outer rotor 51 so as to seal the outer periphery of the outer rotor 51. That is, as the dimensional deviation of the outer rotor 51 due to manufacturing errors or the like is inevitable, the rubber component 80 a produces elastic force which can absorb the dimensional deviation.

The resin component 80 b has a width dimension in the rotational direction of the outer rotor 51 in a manner that there arises a clearance between the resin component 80 b and the concave portion 73 a when the resin component 80 b is arranged in the concave portion 73 a. If the width dimension of the resin component 80 b is made the same as the width dimension of the concave portion 73 a, it becomes difficult to come out when the resin component 80 b enters the concave portion 73 a by flow of the brake fluid pressure at a pump drive time. In the present embodiment, the resin component 80 b is made such that the brake fluid can enter the space between the rubber component 80 a and the resin component 80 b. Therefore, the resin component 80 b can easily come out of the concave portion 73 a with the pressure of brake fluid. The second seal member 81 is also equipped with a rubber component 81 a and a resin component 81 b. Since the second seal member 81 has the same structure as the first seal member 80, the explanation is omitted.

Furthermore, as shown in FIG. 2B, a seal groove part 71 b is defined in the first side plate 71. The seal groove part 71 b has a circular shape (frame shape) surrounding the drive shaft 54, as shown by the single chain line in FIG. 2A. Further, the groove width of the seal groove part 71 b is made large in a predetermined domain, and the seal groove part 71 b is made to communicate with the discharge port 61.

The center of the seal groove part 71 b is positioned eccentrically on a side of the intake port 60 (on a left side of the drawing) with respect to the axial center of the drive shaft 54. The seal groove part 71 b passes through a portion between the discharge port 61 and the drive shaft 54, the maximum and minimum gap portions 53 a and 53 b, and a portion where the first and second seal members 80 and 81 seal the outer circumference gap outside the outer rotor 51.

A seal component 100 is arranged in the seal groove part 71 b. The seal component 100 has an elastic component 100 a made of elastic body such as rubber, and a resin component 100 b made of resin. The resin component 100 b is pressed toward the outer rotor 51 and the inner rotor 52 by the elastic component 100 a.

The resin component 100 b has a circular shape similar to the shape of the seal groove part 71 b. The resin component 100 b has a base part 100 c and a convex part 100 d projected from the base part 100 c on the end surface. The resin component 100 b is arranged in a manner that the convex part 100 d is located on the open side of the seal groove part 71 b, such that the convex part 100 d is in contact with both the outer rotor 51 and the inner rotor 52 and the central plate 73. The elastic component 100 a is arranged on the bottom side of the seal groove part 71 b with respect to the resin component 100 b. Therefore, the resin component 100 b is pressed by the elastic force of the elastic component 100 a and the discharge pressure of the brake fluid introduced into the seal groove part 71 b, such that the seal function is achieved.

The convex part 100 d has a shape shown by the dashed-line hatching in FIG. 2A, and has a sealing part 100 e and a sealing part 100 f. The sealing part 100 e works while the gap portion 53 is shifted from the state communicating with the intake port 60 to the state communicating with the discharge port 61. The sealing part 100 e has a dimension which is able to cover at least the maximum gap portion 53 a on the whole surface so as to tightly seal the maximum gap portion 53 a.

The sealing part 100 f works while the gap portion 53 is shifted from the state communicating with the discharge port 61 to the state communicating with the intake port 60. The sealing part 100 f has a dimension which is able to cover at least the minimum gap portion 53 b on the whole surface so as to tightly seal the minimum gap portion 53 b.

The seal component 100 seals the clearance between the axial end surfaces of the outer rotor 51 and the inner rotor 52 and the first side plate 71, between the high pressure part and the low pressure part. Specifically, the seal component 100 seals the space between the discharge port 61 in the high-pressure state and the gap between the drive shaft 54 and the inner rotor 52 and the intake port 60 in the low-pressure state.

On the other hand, the end surface of the second side plate 72 adjacent to the rotor chamber 50 a is in direct contact with the axial end surfaces of the outer rotor 51 and the inner rotor 52 so as to achieve mechanical sealing. Due to the mechanical sealing, the clearance between the axial end surfaces of the outer rotor 51 and the inner rotor 52 and the second side plate 72 can be sealed between the high pressure part and the low pressure part. Specifically, the space between the discharge port 61 in the high-pressure state and the gap between the drive shaft 54 and the inner rotor 52 and the intake port 60 in the low-pressure state can be sealed by the mechanical sealing.

The seal component 100 located adjacent to the first side plate 71 presses the outer rotor 51 and the inner rotor 52, and the outer rotor 51 and the inner rotor 52 are pressed on the second side plate 72, such that the mechanical sealing is achieved. At this time, because the resin component 100 b of the seal component 100 is pressed by the elastic component 100 a and the discharge pressure of the brake fluid introduced into the seal groove part 71 b, the outer rotor 51 and the inner rotor 52 are pressed on the second side plate 72 at the high pressure. For this reason, the rotation frictional resistance between the outer rotor 51 and the inner rotor 52, and the second side plate 72 becomes large, so the drive torque increases in a conventional art.

According to the present disclosure, as shown in FIGS. 2B and 2C, the second side plate 72 which receives the mechanical sealing has an intake groove 72 b which communicates with the intake port 60 and a discharge groove 72 c which communicates with the discharge port 61. The fluid pressure is introduced from the intake port 60 and the discharge port 61 through the intake groove 72 b and the discharge groove 72 c, respectively, so as to push back the outer rotor 51 and the inner rotor 52. Thus, the frictional resistance is reduced by reducing the force pushing the second side plate 72 by the outer rotor 51 and the inner rotor 52. Accordingly, the increase in the drive torque can be restricted.

The high pressure part and the low pressure part exist on the axial end surfaces of the outer rotor 51 and the inner rotor 52. At the high pressure part, the frictional resistance is reduced by forming the discharge groove 72 c. However, at the low pressure part, the force pushing back the outer rotor 51 and the inner rotor 52 is not enough. Specifically, on the end surfaces of the outer rotor 51 and the inner rotor 52, the brake fluid pressure falls gradually from the discharge groove 72 c in the high pressure state toward the space between the drive shaft 54 and the inner rotor 52 or the intake port 60 in the low pressure state. Therefore, while going from the discharge groove 72 c to the seal components 80 and 81, especially at an area of the outer rotor 51 adjacent to the seal component 80 and 81 relative to the center line Z, the force which puts back the outer rotor 51 toward the seal component 100 becomes small. For this reason, the contact resistance between the outer rotor 51 and the second side plate 72 becomes large.

According to the present embodiment, as shown in FIG. 2C, the end surface of the second side plate 72 is equipped with a concave portion 72 d. Specifically, the concave portion 72 d is formed on the end surface of the second side plate 72 adjacent to the maximum gap portion 53 a relative to the drive shaft 45. When the rotary pump 10 is driven, in response to the rotation of the rotors 51 and 52, the concave portion 72 d is made to communicate with the gap portion 53. More specifically, of the end surface of the second side plate 72, the concave portion 72 d is located in an outer teeth passing section (EXPS), which is shown with the single-chain line in FIG. 3, between a line on which the teeth tip of the outer teeth part 52 a of the inner rotor 52 passes and a line on which the teeth bottom of the outer teeth part 52 a of the inner rotor 52 passes.

In the present embodiment, a plurality of the concave portions 72 d are arranged in the rotational direction of the inner rotor 52, in the outer teeth passing section. Moreover, the concave portion 72 d is located adjacent to the discharge port 61 with respect to the center line Z. The concave portion 72 d is made to communicate with the gap portion 53 where the volume is gradually decreased in response to the rotation of both the rotors 51 and 52, of the plurality of the gap portions 53. The size and the shape of the concave portion 72 d are not limited, but each of the concave portions 72 d has a shape to communicate with only one gap portion 53.

For example, as shown in FIG. 4, if one concave portion 72 d simultaneously communicates with two gap portions 53 located adjacent with each other, the compression performance is lowered in accordance with the volume change in the gap portion 53. For this reason, the size and the shape are set in a manner that each of the concave portions 72 d communicates with only one of the gap portions 53, such that the compression performance can be kept high.

In the present embodiment, the concave portion 72 d extends in the circumferential direction of the inner rotor 52, and the both ends of the concave portion 72 d have circular shape. The width dimension of the concave portion 72 d in the circumferential direction, at this time, is set to be smaller than the teeth width dimension of the inner rotor 52. Thus, each of the concave portions 72 d communicates with only one gap portion 53.

Thus, the concave portion 72 d is defined on the second side plate 72, and the concave portion 72 d is made to communicate with the gap portion 53. For this reason, when the concave portion 72 d and the gap portion 53 communicate with each other, the brake fluid contained in the gap portion 53 is supplied into the concave portion 72 d. Thereby, it becomes possible to make the brake fluid intervene between the second side plate 72 and the inner rotor 52, and the brake fluid functions as lubricating oil. The frictional resistance of the contact part between the second side plate 72 and the inner rotor 52 can be reduced. Therefore, it becomes possible to decrease the amount of wear between the second side plate 72 and the inner rotor 52.

Next, the operations of the brake device and the rotary pump 10 are explained.

For example, at a brake assistance time, the W/C pressure is made larger than the M/C pressure which is generated by operation of the brake pedal 1 by a driver, so as to increase the braking force. In this case, the two-position valve 23 is made in the communicating state suitably, and the differential pressure control valve 22 is operated to produce the pressure difference.

Moreover, the motor 11 is controlled to drive the rotary pump 10, so as to draw and discharge the brake fluid. Specifically, when the motor 11 is driven, the inner rotor 52 is made to rotate according to the rotation of the drive shaft 54. Further, the inner teeth part 51 a and the outer teeth part 52 a mesh with each other, such that the outer rotor 51 is rotated in the same direction. At this time, each volume of the gap portions 53 is increased or decreased while the outer rotor 51 and the inner rotor 52 have one rotation. Therefore, the brake fluid is drawn from the intake port 60, and the brake fluid is discharged out toward the second conduit A2 from the discharge port 61. The W/C pressure is increased by the discharged brake fluid. Thus, fundamental pump operation can be performed with the rotary pump 10, in which brake fluid is drawn from the intake port 60 and is discharged from the discharge port 61 by the rotation of the rotors 51 and 52.

At this time, since the pressure difference control valve 22 is in condition able to generate the pressure difference, the discharge pressure of the rotary pump 10 is applied to the downstream side of the pressure difference control valve 22, i.e., each of the W/C 4 and the W/C 5, such that the W/C pressure can be generated to be larger than the M/C pressure. For this reason, the W/C pressure, which is larger than the M/C pressure generated by operation of the brake pedal 1 by a driver, can be generated with the brake device.

At this time, the outer perimeter of the outer rotor 51 adjacent to the intake port 60 is made to correspond to the intake pressure (atmospheric pressure), due to the brake fluid drawn through the pressure control reservoir 40, and the outer perimeter of the outer rotor 51 adjacent to the discharge port 61 is made to correspond to high discharge pressure.

For this reason, in the outer perimeter of the outer rotor 51, a low pressure portion and a high pressure portion arise. However, as mentioned above, the low pressure portion and the high pressure portion of the outer rotor 51 are separated from each other by the seal components 80 and 81. Therefore, brake fluid can be prevented from leaking toward the low-pressure portion adjacent to the intake port 60 from the high-pressure portion adjacent to the discharge port 61 through the outer perimeter of the outer rotor 51. Moreover, due to the seal components 80 and 81, the outer perimeter of the outer rotor 51 adjacent to the intake port 60 has low pressure which is approximately the same as a pressure in the gap portion 53 which communicates with the intake port 60. Furthermore, the outer perimeter of the outer rotor 51 adjacent to the discharge port 61 has high pressure which is approximately the same as a pressure in the gap portion 53 which communicates with the discharge port 61. For this reason, the pressure balance can be maintained between inside and outside of the outer rotor 51, and the pump can be stably driven.

The seal components 80 and 81 are located adjacent to the intake port 60 in the rotary pump 10 of the present embodiment, so the outer perimeter of the outer rotor 51 has a high discharge pressure up to the position at which the maximum and minimum gap portion 53 a, 53 b is surrounded. For this reason, the outer rotor 51 is pressed in the axial direction, and a load is applied in a direction reducing the teeth tip clearance between the inner teeth part 51 a of the outer rotor 51 and the outer teeth part 52 a of the inner rotor 52, at the maximum gap portion 53 a. Thereby, the brake fluid leak generated through the teeth tip clearance can be reduced.

On the other hand, a clearance between the axial end surface of the inner rotor 52 and the outer rotor 51 and the side plate 71, 72 also has a low pressure portion and a high pressure portion, due to the intake port 60 in the low pressure state, the gap between the drive shaft 54 and the inner rotor 52, and the discharge port 61 in the high pressure state. However, the low pressure portion and the high pressure portion are sealed from each other by the seal component 100 or the mechanical sealing, so brake fluid leak does not occur toward the low pressure portion from the high pressure portion. Moreover, the seal component 100 is formed to overlap the seal components 80 and 81, and the mechanical sealing is formed to be close with the seal components 80 and 81, so brake fluid leak does not occur either.

Since the concave portion 72 d is formed in the end surface of the second side plate 72, when the concave portion 72 d and the gap portion 53 communicate with each other, the brake fluid contained in the gap portion 53 is supplied into the concave portion 72 d. Thereby, it becomes possible to make the brake fluid intervene between the second side plate 72 and the inner rotor 52. The brake fluid functions as lubricating oil, and the frictional resistance of the contact part between the second side plate 72 and the inner rotor 52 can be reduced. Therefore, it becomes possible to decrease the amount of wear between the second side plate 72 and the inner rotor 52.

Furthermore, the concave portion 72 d is located adjacent to the discharge port 61 relative to the center line Z, so it becomes possible to make the concave portion 72 d to communicate with the gap portion 53 in which the volume is decreased, of the plural gap portions 53. For this reason, high pressure brake fluid can be supplied in the concave portion 72 d, and the inner rotor 52 can be pressed back toward the seal component 100 with the high pressure. Therefore, the frictional resistance of the contact part between the second side plate 72 and the inner rotor 52 can be reduced more, and it becomes possible to further decrease the amount of wear between the second side plate 72 and the inner rotor 52.

If the minute clearance S is made to communicate with the concave portion 72 d, high pressure brake fluid is supplied from the minute clearance S into the concave portion 72 d, so the brake fluid pressure of the concave portion 72 d may be made higher. However, when the concave portion 72 d communicates with the gap portion 53 under performing the compression, the volume adjacent to the discharge groove 72 c turns into dead volume, and the compression efficiency falls sharply. For this reason, the concave portion 73 d is made to communicate with only the gap portion 53 without communicating with the minute clearance S.

(Second Embodiment)

In a second embodiment, the frictional resistance is reduced between the second side plate 72 and the outer rotor 51.

As shown in FIG. 5, the end surface of the second side plate 72 is equipped with a concave portion 72 e. Specifically, of the end surface of the second side plate 72, the concave portion 72 e is located adjacent to the maximum gap portion 53 a where the volume becomes the largest relative to the drive shaft 54. When the rotary pump 10 is driven, the concave portion 72 e is made to communicate with the gap portion 53 in response to rotation of the rotors 51 and 52. More specifically, the concave portion 72 e is located in an inner teeth passing section (INPS), shown in the single-chain line in FIG. 6, which is defined between a line on which the teeth tip of the inner teeth part 51 a of the outer rotor 51 passes and a line on which the teeth bottom of the inner teeth part 51 a of the outer rotor 51 passes.

In the inner teeth passing section, a plurality of the concave portions 72 e are arranged in the circumferential direction of the outer rotor 51. Moreover, the concave portion 72 e is located adjacent to the discharge port 61 relative to the center line Z. The concave portion 72 e is made to communicate with the gap portion 53 where the volume is decreased gradually in response to the rotation of both the rotors 51 and 52, of the plurality of the gap portions 53. Similarly to the concave portion 72 d of the first embodiment, the size and the shape of the concave portion 72 e are not limited under the condition that each of the concave portions 72 e communicates with only one gap portion 53.

The concave portion 72 e is shaped to extend along the circumferential direction of the outer rotor 51 e, and both ends of the concave portion 72 e are made circular. The width dimension of the concave portion 72 e in the circumferential direction, at this time, is made to be smaller than the teeth width of the outer rotor 51. Thereby, each of the concave portions 72 e communicates with only one gap portion 53.

Thus, the concave portion 72 e is defined in the second side plate 72, and the concave portion 72 e is made to communicate with the gap portion 53. For this reason, when the concave portion 72 e and the gap portion 53 communicate with each other, the brake fluid contained in the gap portion 53 is supplied in the concave portion 72 e. Thereby, it becomes possible to make the brake fluid intervene between the second side plate 72 and the outer rotor 51, and the brake fluid functions as lubricating oil. The frictional resistance of the contact part between the second side plate 72 and the outer rotor 51 can be reduced. Therefore, it becomes possible to decrease the amount of wear between the second side plate 72 and the outer rotor 51.

As explained above, the concave portion 72 e is formed in the inner teeth passing section of the second side plate 72 through which the inner teeth part 51 a of the outer rotor 51 passes.

(Third Embodiment)

In a third embodiment, the frictional resistance is reduced between the second side plate 72, and the outer rotor 51 and the inner rotor 52.

As shown in FIG. 7, the end surface of the second side plate 72 is equipped with a concave portion 72 f. Specifically, the concave portion 72 f is located adjacent to the minimum gap portion 53 b where the volume becomes the minimum relative to the drive shaft 54. The concave portion 72 f is formed in an overlap area where the inner teeth passing section and the outer teeth passing section overlap with each other. For this reason, when the rotary pump 10 is driven, the concave portion 72 f is made to the communicate with either of the plurality of the gap portions 53 in response to the rotation of both the rotors 51 and 52.

A plurality of the concave portions 72 f are arranged in the circumferential direction of the outer rotor 51 and the inner rotor 52. Moreover, the concave portion 72 f is located adjacent to the discharge port 61 with respect to the center line Z. The concave portion 72 f is formed to communicate with the gap portion 53 where the volume is gradually decreased in response to the rotation of both the rotors 51 and 52, of the plurality of the gap portions 53. Similarly to the concave portion 72 d of the first embodiment, the shape and the size of the concave portion 72 f is not limited under the condition where each of the concave portions 72 f communicates with only one gap portion 53.

The concave portion 72 f is formed to extend in the circumferential direction of the outer rotor 51 and the inner rotor 52, and both ends of the concave portion 72 f are made circular. The width dimension of the concave portion 72 f in the circumferential direction is made to become smaller than the teeth width of the outer rotor 51 and the inner rotor 52. Thereby, each of the concave portions 72 f communicates with only one gap portion 53.

Thus, the concave portion 72 f is defined in the second side plate 72, and the concave portion 72 f is made to communicate with the gap portion 53. For this reason, when the concave portion 72 f and the gap portion 53 communicate with each other, the brake fluid contained in the gap portion 53 is supplied into the concave portion 72 f. Thereby, it becomes possible to make the brake fluid intervene between the second side plate 72, and the outer rotor 51 and the inner rotor 52. The brake fluid functions as lubricating oil. The frictional resistance of the contact part between the second side plate 72, and the outer rotor 51 and the inner rotor 52 can be reduced. Therefore, it becomes possible to decrease the amount of wear between the second side plate 72, and the outer rotor 51 and the inner rotor 52.

The concave portion 72 f is formed adjacent to the minimum gap portion 53 b where the volume becomes the minimum, in the overlap area in which the outer teeth passing section and the inner teeth passing section overlap with each other.

(Other Embodiment)

The shape of the concave portion 72 d-72 f is not limited to the above description, and may be circular, ellipse, oval, or rectangle. The number of the concave portions 72 d-72 f is not limited. The first embodiment to the third embodiment may be suitably combined with each other to provide a mixture of the concave portions 72 d-72 f. The concave portions 72 d-72 f may be located adjacent to the intake port 60 relative to the center line Z, both sides of the center line Z, or on the center line Z.

If the concave portions 72 d-72 f are formed adjacent to the intake port 60 relative to the center line Z, the brake fluid supplied to the concave portion 72 d-72 f may not have high pressure. In this case, the brake fluid functions as lubricating oil, while it may be impossible to press back the outer rotor 51 and the inner rotor 52 toward the seal component 100 with the brake fluid pressure in the concave portion 72 d-72 f.

The casing 50 includes the first side plate 71 in the above embodiment. Alternatively, in a case where components of the rotary pump 10 are accommodated in a housing for an actuator which controls the brake fluid pressure, the housing may constitute the first side plate 71.

The concave portion 72 d is formed in the outer teeth passing section in the first embodiment. However, a part of the concave portion 72 d may be located outside the line on which the teeth bottom of the outer teeth part 52 a passes.

The concave portion 72 e is formed in the inner teeth passing section in the second embodiment. However, a part of the concave portion 72 e may be located outside the line on which the teeth bottom of the inner teeth part 51 a passes.

Such changes and modifications are to be understood as being within the scope of the present disclosure as defined by the appended claims. 

What is claimed is:
 1. A rotary pump comprising: a rotary portion including an outer rotor having an inner teeth part on an inner perimeter, an inner rotor having an outer teeth part on an outer perimeter, the inner rotor having a rotation axis corresponding to a drive shaft, a plurality of gap portions being defined between the inner teeth part and the outer teeth part and having a maximum gap portion which has a maximum volume among the plurality of gap portions; a casing covering the rotary portion and having a first side plate and a second side plate between which the outer rotor and the inner rotor are arranged, the second side plate having a contact surface in contact with the outer rotor and the inner rotor so as to achieve a mechanical sealing, and a central plate arranged to surround an outer perimeter of the outer rotor, the casing having an intake port through which fluid is drawn toward the rotary portion and a discharge port through which fluid is discharged from the rotary portion; and a seal component arranged between the first side plate and the rotary portion to define a low pressure part connected to the intake port and a high pressure part connected to the discharge port, wherein the second side plate has a concave portion on the contact surface adjacent to the maximum gap portion relative to the drive shaft, the concave portion is located in an outer teeth passing section which is defined between a line on which a teeth tip of the outer teeth part of the inner rotor passes in response to rotation of the inner rotor and a line on which a teeth bottom of the outer teeth part of the inner rotor passes in response to rotation of the inner rotor, and the concave portion communicates with one of the plurality of gap portions while the inner rotor is rotated.
 2. The rotary pump according to claim 1, wherein the concave portion communicates with only one of the plurality of gap portions, and does not simultaneously communicate with two of the plurality of gap portions.
 3. The rotary pump according to claim 1, wherein the concave portion has a width dimension in a rotational direction, and the width dimension of the concave portion is smaller than a teeth width dimension of the outer teeth part and the inner teeth part in the rotational direction.
 4. The rotary pump according to claim 1, wherein the outer rotor has a center axis and the inner rotor has a center axis, a center line being defined by connecting the center axis of the outer rotor and the center axis of the inner rotor with each other, and the concave portion is located adjacent to the discharge port with respect to the center line.
 5. A brake device comprising: the rotary pump according to claim 1; a brake fluid pressure generator which generates a brake fluid pressure based on a depression force; a braking force generator which generates a braking force to a wheel based on the brake fluid pressure; a main conduit connected to the brake fluid pressure generator to transmit the brake fluid pressure to the braking force generator; and an auxiliary conduit connected to the brake fluid pressure generator to supply brake fluid to the main conduit so as to raise the braking force generated by the braking force generator, wherein the rotary pump is arranged to draw the brake fluid at the intake port from the brake fluid pressure generator through the auxiliary conduit and to discharge the brake fluid at the discharge port toward the braking force generator through the main conduit.
 6. A rotary pump comprising: a rotary portion including an outer rotor having an inner teeth part on an inner perimeter, an inner rotor having an outer teeth part on an outer perimeter, the inner rotor having a rotation axis corresponding to a drive shaft, a plurality of gap portions being defined between the inner teeth part and the outer teeth part and having a maximum gap portion which has a maximum volume among the plurality of gap portions; a casing covering the rotary portion and having a first side plate and a second side plate between which the outer rotor and the inner rotor are arranged, the second side plate having a contact surface in contact with the outer rotor and the inner rotor so as to achieve a mechanical sealing, and a central plate arranged to surround an outer perimeter of the outer rotor, the casing having an intake port through which fluid is drawn toward the rotary portion and a discharge port through which fluid is discharged from the rotary portion; and a seal component arranged between the first side plate and the rotary portion to define a low pressure part connected to the intake port and a high pressure part connected to the discharge port, wherein the second side plate has a concave portion on the contact surface adjacent to the maximum gap portion relative to the drive shaft, the concave portion is located in an inner teeth passing section which is defined between a line on which a teeth tip of the inner teeth part of the outer rotor passes in response to rotation of the outer rotor and a line on which a teeth bottom of the inner teeth part of the outer rotor passes in response to rotation of the outer rotor, and the concave portion communicates with one of the plurality of gap portions while the inner rotor is rotated.
 7. The rotary pump according to claim 6, wherein the concave portion communicates with only one of the plurality of gap portions, and does not simultaneously communicate with two of the plurality of gap portions.
 8. The rotary pump according to claim 6, wherein the concave portion has a width dimension in a rotational direction, and the width dimension of the concave portion is smaller than a teeth width dimension of the outer teeth part and the inner teeth part in the rotational direction.
 9. The rotary pump according to claim 6, wherein the outer rotor has a center axis and the inner rotor has a center axis, a center line being defined by connecting the center axis of the outer rotor and the center axis of the inner rotor with each other, and the concave portion is located adjacent to the discharge port with respect to the center line.
 10. A brake device comprising: the rotary pump according to claim 6; a brake fluid pressure generator which generates a brake fluid pressure based on a depression force; a braking force generator which generates a braking force to a wheel based on the brake fluid pressure; a main conduit connected to the brake fluid pressure generator to transmit the brake fluid pressure to the braking force generator; and an auxiliary conduit connected to the brake fluid pressure generator to supply brake fluid to the main conduit so as to raise the braking force generated by the braking force generator, wherein the rotary pump is arranged to draw the brake fluid at the intake port from the brake fluid pressure generator through the auxiliary conduit and to discharge the brake fluid at the discharge port toward the braking force generator through the main conduit.
 11. A rotary pump comprising: a rotary portion including an outer rotor having an inner teeth part on an inner perimeter, an inner rotor having an outer teeth part on an outer perimeter, the inner rotor having a rotation axis corresponding to a drive shaft, a plurality of gap portions being defined between the inner teeth part and the outer teeth part and having a minimum gap portion which has a minimum volume among the plurality of gap portions; a casing covering the rotary portion and having a first side plate and a second side plate between which the outer rotor and the inner rotor are arranged, the second side plate having a contact surface in contact with the outer rotor and the inner rotor so as to achieve a mechanical sealing, and a central plate arranged to surround an outer perimeter of the outer rotor, the casing having an intake port through which fluid is drawn toward the rotary portion and a discharge port through which fluid is discharged from the rotary portion; and a seal component arranged between the first side plate and the rotary portion to define a low pressure part connected to the intake port and a high pressure part connected to the discharge port, wherein the second side plate has a concave portion on the contact surface adjacent to the minimum gap portion relative to the drive shaft, the concave portion is located in an overlap area in which an inner teeth passing section and an outer teeth passing section are overlapped with each other, the inner teeth passing section being defined between a line on which a teeth tip of the inner teeth part of the outer rotor passes in response to rotation of the outer rotor and a line on which a teeth bottom of the inner teeth part of the outer rotor passes in response to rotation of the outer rotor, the outer teeth passing section being defined between a line on which a teeth tip of the outer teeth part of the inner rotor passes in response to rotation of the inner rotor and a line on which a teeth bottom of the outer teeth part of the inner rotor passes in response to rotation of the inner rotor, and the concave portion communicates with one of the plurality of gap portions while the inner rotor is rotated.
 12. The rotary pump according to claim 11, wherein the concave portion communicates with only one of the plurality of gap portions, and does not simultaneously communicate with two of the plurality of gap portions.
 13. The rotary pump according to claim 11, wherein the concave portion has a width dimension in a rotational direction, and the width dimension of the concave portion is smaller than a teeth width dimension of the outer teeth part and the inner teeth part in the rotational direction.
 14. The rotary pump according to claim 11, wherein the outer rotor has a center axis and the inner rotor has a center axis, a center line being defined by connecting the center axis of the outer rotor and the center axis of the inner rotor with each other, and the concave portion is located adjacent to the discharge port with respect to the center line.
 15. A brake device comprising: the rotary pump according to claim 11; a brake fluid pressure generator which generates a brake fluid pressure based on a depression force; a braking force generator which generates a braking force to a wheel based on the brake fluid pressure; a main conduit connected to the brake fluid pressure generator to transmit the brake fluid pressure to the braking force generator; and an auxiliary conduit connected to the brake fluid pressure generator to supply brake fluid to the main conduit so as to raise the braking force generated by the braking force generator, wherein the rotary pump is arranged to draw the brake fluid at the intake port from the brake fluid pressure generator through the auxiliary conduit and to discharge the brake fluid at the discharge port toward the braking force generator through the main conduit. 